Jack R. Fraenkel,
San Francisco State UniversityNorman E. Wallen,
San Francisco State University

A-B-A-B design

Same as an A-B-A design, except that a second treatment is added.

A-B-A design

Same as the A-B design except a second baseline is added.

A-B-C-B design

Same as A-B-A-B design except that the second baseline phase is replaced by a modified treatment phase.

A-B design

A single-subject experimental design in which measurements are repeatedly made until stability is presumably established (baseline), after which treatment is introduced and an appropriate number of measurements are made.

Abstract

A summary of a study that describes its most important aspects, including major results and conclusions.

Accessible population

The population from which the researcher can realistically select subjects for a sample, and to which the researcher is entitled to generalize findings.

Achievement test

An instrument used to measure the proficiency level of individuals in given areas of knowledge or skill.

Action plan

A plan to implement change as a result of an action research study.

Action research

A type of research focused on a specific local problem and resulting in an action plan to address the problem.

Age-equivalent score

A score that indicates the age level for which a particular performance (score) is typical.

Alpha coefficient

see Cronbach alpha.

Alternating-treatment design

A single-subject design for studying two or more treatments.

Analysis of covariance (ANCOVA)

A statistical technique for equating groups on one or more variables when testing for statistical significance; it adjust scores on a dependent variable for initial differences on other variables, such as pretest performance or IQ.

Analysis of variance (ANOVA)

A statistical technique for determining the statistical significance of differences among means; it can be used with two or more groups.

Anecdotal records

Records of observed behaviors written down in the form of anecdotes. The best anecdotes tell exactly what the participant did or said without making evaluative statements in the process of reporting this information.

Aptitude test

An instrument used to predict performance in a future situation.

Associational research

A general type of research in which a researcher looks for relationships having predictive and/or explanatory power. Both correctional and causal-comparative studies are examples.

Assumption

Any important assertion presumed to be true but not actually verified; major assumptions should be described in one of the first sections of a research proposal or report.

Attitude scale

A set of statements to which the participant responds.

Average

A number representing the typical score attained by a group of subjects. See measures of central tendency.

B-A-B design

The same as an A-B-A-B design, except that the initial baseline phase is omitted.

Background question

Question asked by an interviewer or on a questionnaire to obtain information about a respondent's background (age, occupation, etc.).

Bar graph

A graphic way of illustrating differences among groups.

Baseline

The graphic record of measurements taken prior to introduction of an intervention in a time-series design.

Behavior questions

See experience questions.

Behavior rating scale

Bias

See researcher bias

Bibliography

A list of references that pertain to a topic.

Biography/biographical study

A form of qualitative research in which the researcher works with the individual to clarify important life experiences

Case study

A form of qualitative research in which a single individual or example is studies through extensive data collection.

Categorical data/variables

Data (variables) that differ only in kind, not in amount or degree.

Causal-comparative research

Research to determine the cause for, or consequences of, existing differences in groups of individuals; also referred to as ex post facto research.

Census

An attempt to acquire data from each and every member of a population.

Chaos theory

A theory and methodology of science that emphasizes the rarity of general laws, the need for very large data bases, and the importance of studying exceptions to overall patterns.

Chi-square test

A non parametric test of statistical significance appropriate when the data are in the form of frequency counts; it compares frequencies actually observed in a study with expected frequencies to see if they are significantly different.

Closed-ended question

A question and a list of alternative responses form which the respondent selects; also referred to as a closed-form item.

Cluster sampling/cluster random sampling

The selection of groups of individuals, called clusters, rather than single individuals. All individuals in a cluster are included in the sample; the clusters are preferably selected randomly from the larger population of clusters.

Coding

The specification of categories in content analysis research. May be done ahead of time or emerge from familiarity with the raw data.

Coefficient of determination (r2)

The square of the correlation coefficient. It indicates the degree of relationship between two variables.

Coefficient of multiple correlation

An index of the strength of the relationship among a combination of predictor variables and the criterion variable. Like the usual correlation coefficient, a coefficient of zero would indicate that the variables are not related. On the other extreme, a coefficient of one would indicate that scores on the criterion variable can be perfectly predicted from the set of predictor variables.

Cohort study

A design (in survey research) in which a particular population is studied over time by taking different random samples at various points in time. The population remains conceptually the same, but individuals change (for example, graduates of San Francisco State University surveyed 10, 20 and 30 years after graduation).

Collective case study

One that studies multiple cases at the same time.

Comparison group

The group in a research study that receives a different treatment from that of the experimental group.

Computer search of the literature

A method whereby key terms are used to locate research literature about a topic.

Concurrent validity (evidence of)

The degree to which the scores on an instrument are related to the scores on another instrument administered at the same time, or to some other criterion available at the same time.

Confidence interval

An interval used to estimate a parameter that is constructed in such a way that the interval has a predetermined probability of including the parameter.

Confirming sample

In qualitative research; a sample selected to validate or extend previous findings.

Constant

A characteristic that has the same value for all individuals.

Constitutive definition

The explanation of the meaning of a term by using other words to describe what is meant.

Construct-related validity (evidence of)

The degree to which an instrument measures an intended hypothetical psychological construct, or nonobservable trait.

Content analysis

A method of studying human behavior indirectly by analyzing communications, usually through a process of categorization.

Content-related validity (evidence of)

The degree to which an instrument logically appears to measure an intended variable; it is determined to expert judgment.

Contextualization

Placing information/data into a larger perspective, especially in ethnography.

Contingency coefficient

An index of relationship derived from a crossbreak table.

Contingency question

A question whose answer depends on the answer to a prior question.

Contingency table

See crossbreak table.

Control

Efforts on the part of the researcher to remove the effects of any variable other than the independent variable that might affect performance on a dependent variable.

Control group

The group in a research study that is treated "as usual."

Convenience sample

A sample that is easily accessible.

Correlational research

Research that involves collecting data in order to determine the degree to which a relationship exists between two or more variables.

Correlation coefficient (r)

A decimal number between .00 and +1.00 and –1.00 that indicates the degree to which two quantitative variables are related.

Counterbalanced design

A design in which all groups receive all treatments. Each group receives the treatments in a different order, and all groups are posttested after each treatment.

Criterion-referenced instrument

An instrument that specifies a particular goal, or criterion, for students to achieve.

Criterion-related evidence of validity (evidence of)

The degree to which performance on an instrument is related to performance on other instruments intended to measure the same variable, or to other variables logically related to the variable being measured.

Criterion variable

The variable that is predicted in a prediction study; also any variables used to assess the criterion-related validity of an instrument.

Critical researchers

Researchers who raise philosophical and ethical questions about the way educational research is conducted.

Critical sample

In qualitative research; a sample considered to be enlightening because it is unusual.

Cronback alpha (_)

An internal consistency or reliability coefficient for an instrument requiring only one test administration.

Crossbreak table

A table that shows all combinations of two or more categorical variables and portrays the relationship (if any) between the variables.

Cross-sectional survey

A survey in which data are collected at one point in time from a predetermined population or populations.

Cross-validation

Validation of a prediction equation with at least one group other than the group on which it was based.

Crystallization

Occasions, especially in ethnography, when different kinds of data 'fall in place' to make a coherent picture.

Culture

The sum of a social group's observable patterns of behavior and/or their customs, beliefs and knowledge.

Curvilinear relationship

A relationship shown in a scatterplot in which the line that best fits the points is not straight.

Data

Any information obtained about a sample or a population.

Data analysis

The process of simplifying data in order to make it comprehensible.

Degrees of freedom

A number indicating how many instances out of a given number of instance are "free to vary" _ that is, not predetermined.

Demographics

Characteristics of a sample or population (e.g., age, ethnicity, education).

Dependent variable

A variable affected or expected to be affected by the independent variable; also called "criterion" or "outcome variable."

Derived scores

A score obtained from a raw score in order to aid in interpretation. Derived scores provide a quantitative measure of each student's performance relative to a comparison group.

Descriptive field notes

Notes that describe what the researcher has observed.

Descriptive studies

Research to describe existing conditions without analyzing relationships among variables.

Descriptors

Terms used to locate sources during a computer search of the literature.

Directional hypothesis

A relational hypothesis stated in such a manner that a direction, often indicated by "greater than" or "less than," is hypothesized for the results.

Discriminant function analysis

A statistical procedure for predicting group membership (a categorical variable) from two or more quantitative variables.

Ecological generalizibility

The degree to which results can be generalized to environments and conditions outside the research setting.

Educational Resources Information Center (ERIC)

Effect size (ES)

An index used to indicate the magnitude of an obtained result or relationship.

Emic perspective

The view of reality of a cultural 'insider'; especially in ethnography.

Empirical

Based on observable evidence.

Equivalent forms

Two tests identical in every way except for the actual items included.

Equivalent-forms method

A method to obtain to reliability coefficient; a way of checking consistency by correlating scores on equivalent forms of an instrument. It is also referred to as alternate-forms reliability.

Errors of measurement

Inconsistency of individual scores on the same instrument.

Eta (_)

An index that indicates the degree of a curvilinear relationship.

Ethnography/ethnographic research

The collection of data on many variables over an extended period of time in a naturalistic setting, usually using observation and interviews.

Etic perspective

The 'outsider' or 'objective' view of a culture's reality, especially in ethnography.

Expectancy table

A table used to analyze data obtained from a categorical variable and a criterion that is categorical.

Experience questions

Questions a researcher asks to find out what sorts of things an individual is doing or has done.

Experiment

A research study in which one or more independent variables is systematically varied by the researcher to determine the effects of this variation.

Experimental group

The group in a research study that receives the treatment (or method) of special interest in the study.

Experimental research

Research in which at least one independent variable is manipulated, other relevant variables are controlled, and the effect on one of more dependent variables is observed.

Experimental variable

The variable that is manipulated (systematically altered) in an intervention study by the researcher.

Explanatory mixed method design

A study in which quantitative data are collected first and findings tested with subsequent quantitative data.

Exploratory mixed method design

A study in which qualitative data are collected first and further clarified with qualitative data.

External audit

An individual outside the study is asked to review the methods and interpretations of a qualitative study.

External criticism

Evaluation of the genuineness of a document in historical research.

External validity

The degree to which results are generalizable, or applicable, to groups and environments outside the research setting.

External validity of single-subject studies

Extraneous event(s)

See history threat.

Extraneous variable

A variable that makes possible an alternative explanation of results; an uncontrolled variable.

Extraneous variable

A variable that makes possible an alternative explanation of results; an uncontrolled variable.

Factor analysis

A statistical method for reducing a set of variables to a smaller number of factors.

Factorial design

An experimental design that involves two or more independent variables (at least one of which is manipulated) in order to study the effects of the variables individually, and in interaction with each other, upon a dependent variable.

Feelings questions

Questions researchers ask to find out how people feel about things.

Field diary

A personal statement of a researcher's opinions about people and events he or she comes in contact with during research.

Field jottings

Quick notes taken by an ethnographer.

Field log

A running account of how an ethnographer plans to, and actually does, spend his or her time in the field.

Field notes

The notes researchers take about what they observe and think about in the field.

Findings

see results (of a study).

Five-number summary

Consists of the lowest score, the first quartile, the median, the third quartile, and the highest score. This summary provides a quick overview about the central tendency, variability, and shape of the distribution with just five numbers.

Flowchart

Types of tally sheets used to indicate the frequency and direction of a participant's remarks.

Focus group interview

An interview conducted with a group in which respondents hear the views of each other.

Follow-up study

A study conducted to determine the characteristics of a group after some period of time.

Foreshadowed problems

The problem or topic that serves, in a general way, as the focus for a qualitative inquiry.

Frequency distribution

A tabular method of showing all the scores obtained by a group of individuals.

Frequency polygon

A graphic method of showing all of the scores obtained by a group of individuals.

Friedman two-way analysis of variance

A nonparametric inferential statistic used to compare two or more groups that are not independent.

Gain score

The difference between the pretest and posttest scores of a measure.

Generalizing

See ecological generalizibility; population generalizability.

General references

Sources that researchers use to identify more specific references (e.g., indexes, abstracts).

Grade-equivalent score

A score that indicates the grade level for which a particular performance (score) is typical.

Grounded theory

A form of qualitative research which derives interpretations inductively from raw data with continual interplay between data and emerging interpretations.

Hawthorne effect

A positive effect of an intervention resulting from the subjects' knowledge that they are involved in a study or their feeling that they are in some way receiving "special" attention.

Histogram

A graphic representation, consisting of rectangles, of the scores in a distribution; the height of each rectangle indicates the frequency of each score, or group of scores.

Historical research

The systematic collection and objective evaluation of data related to past occurrences to determine causes, effects, or trends of those events that may help explain present events and anticipate future events.

History threat

The possibility that results are due to an event that is not part of an intervention, but which may affect performance on the dependent variable, thereby affecting internal validity.

Holistic perspective

The attempt to incorporate all aspects of a culture into an ethnographic interpretation.

Homogeneous sample

In qualitative research, a sample selected in which all members are similar with respect to one or more characteristics.

Hypothesis

A tentative, testable assertion regarding the occurrence of certain behaviors, phenomena, or events; a prediction of study outcomes.

Implementation threat

The possibility that results are due to variations in the implementation of the treatment in an intervention study, thereby affecting internal validity.

Independent variable

A variable that affects (or is presumed to affect) the dependent variable under study and is included in the research design so that its effect can be determined; sometimes called the "experimental" or "treatment" variable.

Inferential statistics

Data analysis techniques for determining how likely it is that results based on a sample or samples are similar to results that would have been obtained for the entire population.

Informal interviews

Less-structured form of interview, usually conducted by qualitative researchers. They do not involve any specific type or sequence of questioning, but resemble more the give and take of a casual conversation.

Instrument

Any device for systematically collecting data, such as a test, a questionnaire, or an interview schedule.

Instrumental case study

One that focuses on a particular individual or situation with little effort to generalize.

Instrumentation

Instruments and procedures used in collecting data in a study.

Instrumentation threat

The possibility that results are due to variations in the way data are collected, thereby affecting internal validity.

Instrument decay

Changes in instrumentation over time that may affect the internal validity of a study.

Interaction

An effect created by unique combinations of two or more independent variables; systematically evaluated in a factorial design.

Interjudge reliability

The consistency of two (or more) independent scorers, raters, or observers.

Internal-consistency methods

Procedures for estimating reliability of scores using only one administration of the instrument.

Internal criticism

Determining if the contents of a document are accurate.

Internal validity

The degree to which observed differences on the dependent variable are directly related to the independent variable, not to some other (uncontrollable) variable.

Interval scale

A measurement scale that, in addition to ordering scores from high to low, also establishes a uniform unit in the scale so that equal distance between two scores is of equal magnitude.

Intervention

A specified treatment or method that is intended to modify one or more dependent variables.

Intervention study/research

A general type of research in which variables are manipulated in order to study the effect on one of more dependent variables.

Interview

A form of data collection in which individuals or groups are questioned orally.

Intrinsic case study

One that attempts to generalize beyond the particular case.

Item validity

The degree to which each of the items in an instrument measures the intended variable.

Justification (of a study)

A rationale statement in which a researcher indicates why the study is important to conduct; includes implications for theory and/or practice.

Questions interviewers ask to find out what factual information a respondent possesses about a particular topic.

Kruskal-Wallis one-way analysis of variance

A nonparametric inferential statistic used to compare two or more independent groups for statistical significance of differences.

Kuder-Richardson approaches

Procedures for determining an estimate of the internal consistency reliability of a test or other instrument from a single administration of the test without splitting the test into halves.

Latent content

The underlying meaning of a communication.

Level of confidence

The probability associated with a confidence interval; the probability that the interval will contain the corresponding parameter. Commonly used confidence levels in educational research are the 95 and 99 percent confidence levels.

Level of significance

The probability that a discrepancy between a sample statistic and a specified population parameter is due to sampling error, or chance. Commonly used significance levels in educational research are .05 and .01.

Likert scale

A self-reporting instrument in which an individual responds to a series of statements by indicating the extent of agreement. Each choice is given a numerical value, and the total score is presumed to indicate the attitude or belief in question.

Limitation

An aspect of a study that the researcher knows may influence the results or generalizability of the results, but over which he or she has no control.

Linear relationship

A relationship in which an increase (or decrease) in one variable is associated with a corresponding increase (or decrease) in another variable.

Literature review

The systematic identification, location, and analysis of documents containing information related to a research problem.

Location threat

The possibility that results are due to characteristics of the setting or location in which a study is conducted, thereby producing a threat to internal validity.

Logic

Using knowledge to create new knowledge.

Longitudinal survey

A study in which information is collected at different points in time in order to study changes over time (usually of considerable length, such a several months or years).

Manifest content

The obvious meaning of a communication.

Manipulated variable

See experimental variable.

Mann-Whitney U test

A nonparametric inferential statistic used to determine whether two uncorrelated groups differ significantly.

Matching

Consists of two groups of items listed in columns. Respondents are required to match the item in the left column that corresponds most closely with an item in the right column.

Matching design

A technique for equating groups on one or more variables, resulting in each member of one group having a direct counterpart in another group.

Maturation threat

The possibility that results are due to changes that occur in subjects as a direct result of the passage of time and that may affect their performance on the dependent variable, thereby affecting internal validity.

Maximal variation sample

In qualitative research, a sample selected in order to represent diversity in one or more characteristics.

Mean/arithmetic mean

The sum of the scores in a distribution divided by the number of scores in the distribution; the most commonly used measure of central tendency.

Measures of central tendency

Indices representing the average or typical score attained by a group of subjects; the most commonly used in educational research are the mean and the median.

Measures of variability

Indices indicating how spread out the scores are in a distribution. Those most commonly used in educational research are the range, standard deviation, and variance.

Mechanical matching

A process of pairing two persons whose scores on a particular variable are similar.

Median

That point in a distribution having 50 percent of the scores above it and 50 percent of the scores below it.

Member checking

Participants in a qualitative study are asked to check the accuracy of the research report.

Meta-analysis

A statistical procedure for combining the results of several studies on the same topic.

Mixed-method design

A study combining quantitative and qualitative methods.

Mode

The score that occurs most frequently in a distribution of scores.

Moderator variable

A variable that may or may not be controlled but has an effect on the research situation.

Mortality threat

The possibility that results are due to the fact that subjects who are for whatever reason "lost" to a study may differ from those who remain so that their absence has an important effect on the results of the study.

Multiple analysis of covariance (MANCOVA)

An extension of analysis of covariance that incorporates two or more dependent variables in the same analysis.

Multiple-baseline design

A single-subject experimental design in which baseline data are collected on several behaviors for one subject, after which the treatment is applied sequentially over a period of time to each behavior one at a time until all behaviors are under treatment. Also used to collect data on different subjects with regard to a single behavior, or to assess a subject's behavior in different settings.

Multiple correlation (R)

A numerical index describing the relationship between predicted and actual scores using multiple regression. The correlation between a criterion and the "best combination" of predictors.

Multiple perspectives

The recognition and acceptance of multiple views of reality, especially in ethnography.

Multiple regression

A technique using a prediction equation with two or more variables in combination to predict a criterion (y = a + b1X1 + b2X2 + b3X3…).

Multiple-treatment interference

The carryover or delayed effects of prior experimental treatments when individuals receive two or more experimental treatments in succession.

Naturalistic observation

Observation in which the observer controls or manipulates nothing, and tries not to affect the observed situation in any way.

Natural setting

A specific place in which events and interactions among individuals typically occur.

Negatively skewed distribution

A distribution in which there are more extreme scores at the lower end than at the upper, or higher, end.

Nominal scale

A measurement scale that classifies elements into two or more categories, the numbers indicating that the elements are different, but not according to order or magnitude.

Nondirectional hypothesis

A prediction that a relationship exists without specifying its exact nature.

Nonequivalent control group design

An experimental design involving at least two groups, both of which may be pretested; one group receives the experimental treatment, and both groups are posttested. Individuals are not randomly assigned to treatments.

Nonparametric technique

A test of statistical significance appropriate when the data represent an ordinal or nominal scale, or when assumptions required for parametric tests cannot be met.

Nonparticipant observation

Observation in which the observer is not directly involved in the situation to be observed

Nonrandom sample/sampling

The selection of a sample in which every member of the population does not have an equal chance of being selected.

Normal distribution

A theoretical "bell-shaped" distribution having a wide application to both descriptive and inferential statistics. It is known or thought to portray many human characteristics in "typical" populations.

Norm group

The sample group used to develop norms for an instrument.

Norm-referenced instrument

An instrument that permits comparison of an individual score to the scores of a group of individuals on the same instrument.

Norms

Descriptive statistics that summarize the test performance of a reference group of individuals and permit meaningful comparison of individuals to the group.

Null hypothesis

A statement that any difference between obtained sample statistics and specified population parameters is due to sampling error, or "chance."

Objectivity

A lack of bias or prejudice.

Observational data

Data obtained through direct observation.

Observer bias

The possibility that an observer does not observe objectively and accurately, thus producing invalid observations and a threat to the internal validity of a study.

Observer effect

The impact of an observer's presence on the behavior observed.

Observer expectations

The effect that an observer's prior information can have on observational data.

One-group pretest-posttest design

A weak experimental design involving one group that is pretested, exposed to a treatment, and posttested.

One-shot case study design

A weak experimental design involving one group that is exposed to a treatment and then posttested.

One-tailed test

The use of only one tail of the sampling distribution of statistic – used when a directional hypothesis is stated.

Open-ended question

A question giving the responder complete freedom of response.

Operational definition

Defining a term by stating the actions, processes, or operations used to measure or identify examples of it.

Opinion questions

Questions a researcher asks to find out what people think about a topic.

Opportunistic sample

In qualitative research, a sample chosen to take advantage of conditions that arise during a study.

Oral statements

Some form of oral expression.

Ordinal scale

A measurement scale that ranks individuals in terms of the degree to which they possess a characteristic of interest.

Outcome variable

See dependent variable.

Outlier

Scores or other observations that deviate or fall considerably outside most of the other scores or observation in a distribution or pattern.

Panel study

A longitudinal design (in survey research) in which the same random sample is measured at different points in time.

Parameter

A numerical index describing a characteristic of a population.

Parametric technique

A test of significance appropriate when the data represent an interval or ratio scale of measurement and other specific assumptions have been met.

Partial correlation

A method of controlling the subject characteristics threat in correlational research by statistically holding one or more variables constant.

Participant observation

Observation in which the observer actually becomes a participant in the situation to be observed.

Participants

Individuals whose involvement in a study can range from providing data to initiating and designing the study.

Participatory action research

Action research intended not only to address a local problem but also to empower individuals and to bring about social change.

An index of correlation appropriate when the data represent either internal or ratio scales; it takes into account each and every pair of scores and produces a coefficient between .00 and either + or – 1.00.

Percentile rank

An index of relative position indicating the percentage of scores that fall at or below a given score.

Performance checklist

Used to keep track of behaviors that occur.

Performance test

Measures an individual's performance on a particular task.

Phenomenology/phenomenological research

A form of qualitative research in which the researcher attempts to identify commonalilties in the perceptions of several individuals regarding a particular phenomenon.

Pie chart

A graphic method of displaying the breakdown of data into categories.

Pilot study

A small-scale study administered before conducting an actual study _ its purpose is to reveal defects in the research plan.

Population

The group to which the researcher would like the results of a study to be generalizable; it includes all individuals with certain specified characteristics.

Population generalizability

The extent to which the results obtained from a sample are generalizable to a larger group.

Portraiture

A form of qualitative research in which the researcher and the individual being portrayed work together to define meaning.

Positively skewed distribution

A distribution in which there are more extreme scores at the upper, or higher, end than at the lower end.

Positivism

A philosophic viewpoint emphasizing an 'objective' reality which includes universal laws governing all things including human behavior.

Posttest-only control group design

An experimental design involving at least two randomly formed groups; one group receives a treatment, and both groups are posttested.

Power of a statistical test

The probability that the null hypothesis will be rejected when there is a difference in the populations; the ability of a test to avoid a Type II error.

Practical action research

Action research intended to address a specific local problem.

Practical significance

A difference large enough to have some practical effect. Contrast with statistical significance, which may be so small as to have no practical consequences.

Predicted score

The score a researcher predicts that someone will obtain when measured on one variable after it is known what score the person obtained when measured on another variable.

Prediction

The estimation of scores on one variable from information about one or more other variables.

Prediction equation

A mathematical equation used in a prediction study.

Prediction equation

A mathematical equation used in a prediction study.

Prediction studies

Attempts to determine variables that are related to a criterion variable.

Prediction study

An attempt to determine variables that are related to a criterion variable.

Predictive validity (evidence of)

The degree to which scores on an instrument predict characteristics of individuals in a future situation.

Predictor variable

The variable from which projections are made in a prediction study.

Predictor variable(s)

The variable(s) from which projections are made in a prediction study.

Pretest-posttest control group design

An experimental design that involves at least two groups; both groups are pretested, one group receives a treatment, and both groups are posttested. For effective control of extraneous variables, the groups should be randomly formed.

Pretest-treatment interaction

The possibility that subjects may respond or react differently to a treatment because they have been pretested, thereby creating a threat to internal validity.

Primary source

Firsthand information such as the testimony of an eyewitness, an original document, a relic, or a description of a study written by the person who conducted it.

Primary source

Firsthand information such as the testimony of an eyewitness, an original document, a relic, or a description of a study written by the person who conducted it.

Probability

The relative frequency with which a particular event occurs among all events of interest.

Problem statement

A statement that indicates the specific purpose of the research, the variables of interest to the researcher, and any specific relationship between those variables that is to be, or was, investigated; includes description of background and rationale (justification) for the study.

Procedures

A detailed description by the researcher of what was (or will be) done in carrying out a study.

Purpose (of a study)

A specific statement by a researcher of what he or she intends to accomplish.

Purposive sample

A nonrandom sample selected because prior knowledge suggests it is representative, or because those selected have the needed information.

Qualitative data

Data that are not numerical.

Qualitative research/study

Research in which the investigator attempts to study naturally occurring phenomena in all their complexity.

Qualitative variable

A variable that is conceptualized and analyzed as distinct categories, with no continuum implied.

Quantitative data

Data that differ in amount or degree, along a continuum from less to more.

Quantitative research

Research in which the investigator attempts to clarify phenomena through carefully designed and controlled data collection and analysis.

Quantitative variable

A variable that is conceptualized and analyzed as distinct categories, with no continuum implied.

Quasi-experimental designs

A type of experimental design in which the researcher does not use random assignment of subjects to groups.

Questionnaire

A list of questions that the participant answers in writing or by marking answers on an answer sheet.

Random assignment

The process of assigning individuals or groups randomly to different treatment conditions.

Random numbers, table of

A table of numbers that provides one of the best means of random selection or random assignment.

Random sample

A sample selected in such a way that every member of the population has an equal chance of being selected.

Random sampling

Methods designed to select a representative sample by using chance selection so that biases will not systematically alter the sample.

Random selection sampling

The process of selecting a random sample.

Range

The difference between the highest and lowest scores in a distribution; measure of variability.

Rating scale

The rating scale is an instrument on which a researcher or participant or observer can record a rating of a behavior, a product, or a performance.

Ratio scale

A measurement scale that, in addition to being an interval scale, also has an absolute zero in the scale.

Raw score

The score attained by an individual on the items on a test or other instrument.

Reflective field notes

A record of the observer's thoughts and reflections during and after observation.

Regressed gain score

A score indicating amount of change that is determined by the correlation between scores on a posttest and a pretest (and/or other scores). It provides more stable information than a simple posttest-pretest difference.

Regression line

The line of best fit for a set of scores plotted on coordinate axes (on a scatterplot).

Regression threat

The possibility that results are due to a tendency for groups, selected on the basis of extreme scores, to regress toward a more average score on subsequent measurements, regardless of the experimental treatment.

Relationship

A connection between two qualities or characteristics (e.g., motivation and learning).

Relationship study

A study investigating relationships among two or more variables, one of which may be a treatment (method) variable.

Reliability

The degree to which scores obtained with an instrument are consistent measures of whatever the instrument measures.

Reliability coefficient

An index of the consistency of scores on the same instrument. There are several methods of computing a reliability coefficient, depending on the type of consistency and characteristics of the instrument.

Relics

Any object that can provide some information about the past.

Replication

Refers to conducting a study again; the second study may be a repetition of the original study, using different subjects, or may change specified aspects of the study.

Representativeness

The extent to which a sample is identical (in all characteristics) to the intended population.

Representative sample

A sample that is like the population in terms of relevant characteristics.

Research

The formal, systematic application of scholarship, disciplined inquiry, and most often the scientific method to the study of problems.

Research bias

see threat to internal validity.

Research design

The overall plan for collecting data in order to answer the research question. Also the specific data analysis techniques or methods that the researcher intends to use.

Researcher bias

A situation in which the researcher's hopes or expectations concerning the outcomes of the study actually contribute to producing various outcomes, thereby creating a threat to internal validity.

Research hypothesis

A prediction of study outcomes. Often a statement of the expected relationship between two or more variables.

Research problem

A problem that someone would like to research; it is the focus of a research investigation.

Research proposal

A detailed description of a proposed study designed to investigate a given problem.

Research question

A question that we can answer by collecting and analyzing data.

Research report

A description of how a study was conducted, including results and conclusions.

Results (of a study)

A statement that explains what is shown by analysis of the data collected; includes tables and graphs when appropriate.

Retrospective interview

A form of interview in which the researcher tries to get a respondent to reconstruct past experiences.

Sample

The group on which information is obtained.

Sampling

The process of selecting a number of individuals (a sample) from a population, preferably in such a way that the individuals are representative of the larger group from which they were selected.

Sampling distribution

The theoretical distribution of all possible values of a statistic from all possible samples of a given size selected from a population.

Sampling error

Expected, chance variation in sample statistics that occurs when successive samples are selected for the sample in systematic sampling.

Sampling interval

The distance in a list between individuals chosen when sampling systematically.

Scatterplot

The plot of points determined by the cross-tabulation of scores on coordinate axes; used to represent and illustrate the relationship between two quantitative variables.

Scientific method

A way of knowing that it is characterized by the public nature of its procedures and conclusions and by rigorous testing of conclusions.

Search terms

see descriptors.

Secondary source

Secondhand information, such as a description of historical events by someone not present when the event occurred.

Self-checklist

A list of characteristics or activities that the participants in a study reads and then checks to identify those characteristics that they possess or the activities that they have engaged in.

Semistructured interview

A structured interview, combined with open-ended questions.

Sensory questions

Questions asked by a researcher to find out what a person has seen, heard, or experienced through his or her senses.

Short-answer items

A type of supply item in which the respondent is required to supply a word, phrase, number, or symbol that is necessary to complete a statement or answer the question.

Sign test

A nonparametric inferential statistic used to compare two groups that are not independent.

Simple random sample

see random sample.

Simulation

Research in which an "artificial" situation is created and participants are told what activities they are to engage in.

Single-subject designs

Designs applied when the sample size is one; used to study the behavior change that an individual exhibits as a result of some intervention or treatment.

Single-subject research

Research that focuses on individual study participants, rather than groups.

Skewed distribution

A nonsymmetrical distribution in which there are more extreme scores at one end of the distribution than the other.

Snowball sample

In qualitative research, a sample selected as the need arises during a study.

Split-half procedure

A method of estimating the internal-consistency reliability of an instrument; it is obtained by giving an instrument once but scoring it twice – for each of two equivalent "half tests." These scores are then correlated.

Stability

The extent to which scores are reliable (consistent) over time.

Standard deviation (SD)

The most stable measure of variability; it takes into account each and every score in a distribution

Standard error of a statistic

The standard deviation of the sampling distribution of a statistic.

Standard error of estimate

An estimate of the size of the error to be expected in predicting a criterion score.

Standard error of measurement (SEMeas)

An estimate of the size of the error that one can expect in an individual's score.

Standard error of the difference (SED)

The most stable measure of variability; it takes into account each and every score in a distribution..

Standard error of the difference between means

Standard error of the mean (SEM)

The standard deviation of sample means that indicates by how much the sample means can be expected to differ if other samples from the same population are used.

Standard score

A derived score that expresses how far a given raw score is from the mean, in terms of standard deviation units.

Static-group comparison design

A weak experimental design that involves at least two nonequivalent groups; one receives a treatment and both are posttested.

Static-group pretest-posttest design

The same as the static-group comparison design, except that both groups are pretested.

Statistic

A numerical index describing a characteristic of a sample.

Statistical equating

see statistical matching.

Statistically significant

The conclusion that results are unlikely to have occurred due to sampling error or "chance;" an observed correlation or difference probably exists in the population.

Statistical matching

A means of equating groups using statistical prediction.

Statistical regression threat

see regression threat.

Statistics

A numerical index describing a characteristic of a sample.

Stratified random sampling

The process of selecting a sample in such a way that identified subgroups in the population are represented in the sample in the same proportion as they exist in the population.

Structured interview

A formal type of interview, in which the researcher asks, in order, a set of predetermined questions.

Subject characteristics threat

The possibility that characteristics of the subjects in a study may account for observed relationships, thereby producing a threat to internal validity.

Subjects

Individuals whose participation in a study is limited to providing information.

Survey

A method of collecting information by asking a sample of participants questions in order to find out information about a population.

Survey study/research

An attempt to obtain data from members of a population (or a sample) to determine the current status of that population with respect to one or more variables.

Systematic sampling

A selection procedure in which all sample elements are determined after the selection of the first element, since each element on a selected list is separated from the first element by a multiple of the selection interval.

Table of random numbers

A table of numbers that provides one of the best means of random selection or random assignment.

Tally sheet

A device used by researchers to report the frequency of student behaviors, activities, or remarks.

Target population

The population to which the researcher, ideally, would like to generalize results.

Testing threat

A threat to internal validity that refers to improved scores on a posttest that are a result of subjects having taken a pretest.

Test of significance

A statistical test used to determine whether or not the obtained results for a sample are likely to represent the population.

Test-retest method

A procedure for determining the extent to which scores from an instrument are reliable over time by correlating the scores from two administrations of the same instrument to the same individuals.

Theme

A means of organizing and interpreting data in a content analysis by grouping codes as the interpretation progresses.

Theoretical sample

In qualitative research, a sample that helps the researcher understand or formulate a concept or interpretation.

Thick description

In ethnography, the provision of great detail on the basic data/information.

Thick description

In ethnography, the provision of great detail on the basic data/information.

Time-and-motion logs

Reporting of what is observed and the time it is observed.

Time-series design

An experimental design involving one group that is repeatedly pretested, exposed to an experimental treatment, and repeatedly posttested.

Treatment variable

see experimental variable.

Trend study

A longitudinal design (in survey research) in which the same population (conceptually but not literally) is studied over time by taking different random samples.

A study in which quantitative and qualitative data are collected simultaneously and used to validate and clarify findings.

True-false item

A statement that is either true or false and the respondent must indicate which it is.

T score

A standard score derived from a z score by multiplying the z score by 10 and adding 50.

t-test for correlated means

A parametric test of statistical significance used to determine whether there is a statistically significant difference between the means of two matched, or nonindependent, samples. It is also used for pre-post comparisons.

t-test for correlated proportions

A parametric test of statistical significance used to determine whether there is a statistically significant difference between two proportions based on the same sample or otherwise non-independent groups.

t-test for independent means

A parametric test of significance used to determine whether there is a statistically significant difference between the means of two independent samples.

t-test for independent proportions

A parametric test of statistical significance used to determine whether there is a statistically significant difference between two independent proportions.

t-test for means

A parametric technique for comparing two means.

t-test for r

A parametric technique for determining if there is a non-zero correlation among two variables in the population.

Two-stage random sampling

A process in which clusters are first randomly selected and then individuals are selected from each cluster.

Two-tailed test

Use of both tails of the sampling distribution of a statistic – when a nondirectional hypothesis is stated.

Type I error

The rejection by the researcher of a null hypothesis that is actually true. Also called alpha error.

Type II error

The failure of a researcher to reject a null hypothesis that is really false. Also called beta error.

Typical sample

In qualitative research, a sample judged to be representative of the population of interest.

Unit of analysis

The unit that is used in data analysis (individuals, objects, groups, classrooms, etc.).

Unobtrusive measures

Measures obtained without subjects being aware that they are being observed or measured, or by examining inanimate objects (such as school suspension lists) that can be used in order to obtain desired information.

Validity

The degree to which correct inferences can be made based on results from an instrument; depends not only on the instrument itself, but also on the instrumentation process and the characteristics of the group studied.

Validity coefficient

An index of the validity of scores; a special application of the correlation coefficient.

Values questions

see opinion questions.

Variability

The extent to which scores differ from one another.

Variable

A characteristic that can assume any one of several values, for example, cognitive ability, height, aptitude, teaching method.

Variance (SD2)

The square of the standard deviation; a measure of variability.

Wilk's lambda

The numerical index calculated when carrying out MANOVA or MANCOVA.

z-score

The most basic standard score that expresses how far a score is from a mean in terms of standard deviation units